Production of high-viscosity oil at Boca de Jaruco field (the Republic of Cuba) involves operation of horizontal steam injection wells under cyclic temperatures of 25-300°C, H2S and CO2 action. Based on the described conditions, cement is required to maintain compressive and bending strength. Specialists of Giprovostokneft selected cement composition and carried out a research to confirm its compliance with the requirements for steam injection wells under H2S and CO2 action. When defining requirements to cementing for Boca de Jaruco steam injection wells, we performed computer modeling of static and dynamic loads during operation in casing pipe – set cement – formation system. ANSYS software was used for finite element modeling. As a result of modeling, loads on set cement were determined when casing pipe was heated to maximum temperature during steam injection and casing pipe expansion. The most significant factor to determine set cement strength behind casing pipe is its bending strength. For Boca de Jaruco wells, minimum required set cement bending strength is 6.8 MPa. Insufficient bending strength of set cement increases the risk of cement fracturing and formation of radial cracks caused by expansion of casing pipe during steam injection. Standard plugging materials were tested in H2S and CO2 environments and at temperature varied from 25 to 300°C. It was found during the research that bending strength of test samples was less than 6.8 MPa that is minimum required strength of set cement for this field. In this regard, a new composition of plugging material including 85% of Portland cement PCT-I-G-CC-1, 10% of quartz flour and 5% of fly ash has been developed in Giprovostokneft test laboratory center. It was found that after simultaneous exposure to changed temperature (5 cycles of 25-300°C) and H2S and CO2, the bending strength was 8.5 MPa, which meets the requirements determined by computer modeling. The developed plugging material was used in three Boca de Jaruco wells BJ-3004, BJ-3005, BJ-3006 for production casing cementing. According to cement bond logging results, areas having micro-damage of set cement, accumulations of water and gas are close to nonexistent. Cement quality factors determined by USIT fall were 0.88 - 0.93.
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